package com.young.security.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Base64字符串与字节码转换工具
 *
 * @author steven-pan
 */
public class Base64 {
  private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
  
  /**
   * data[]进行编码
   *
   * @param data
   * @return
   */
  public static String encode(byte[] data) {
    int start = 0;
    int len = data.length;
    StringBuffer buf = new StringBuffer(data.length * 3 / 2);
    
    int end = len - 3;
    int i = start;
    int n = 0;
    
    while (i <= end) {
      int d = ((((int) data[i]) & 0x0ff) << 16)
          | ((((int) data[i + 1]) & 0x0ff) << 8)
          | (((int) data[i + 2]) & 0x0ff);
      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append(legalChars[d & 63]);
      i += 3;
      if (n++ >= 14) {
        n = 0;
        buf.append(" ");
      }
    }
    
    if (i == start + len - 2) {
      int d = ((((int) data[i]) & 0x0ff) << 16)
          | ((((int) data[i + 1]) & 255) << 8);
      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append("=");
    } else if (i == start + len - 1) {
      int d = (((int) data[i]) & 0x0ff) << 16;
      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append("==");
    }
    
    return buf.toString();
  }
  
  private static int decode(char c) {
    if (c >= 'A' && c <= 'Z') {
      return ((int) c) - 65;
    } else if (c >= 'a' && c <= 'z') {
      return ((int) c) - 97 + 26;
    } else if (c >= '0' && c <= '9') {
      return ((int) c) - 48 + 26 + 26;
    } else {
      switch (c) {
        case '+':
          return 62;
        case '/':
          return 63;
        case '=':
          return 0;
        default:
          throw new RuntimeException("unexpected code: " + c);
      }
    }
  }
  
  /**
   * Decodes the given Base64 encoded String to a new byte array. The byte
   * array holding the decoded data is returned.
   */
  
  public static byte[] decode(String s) {
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    try {
      decode(s, bos);
    } catch (IOException e) {
      throw new RuntimeException();
    }
    byte[] decodedBytes = bos.toByteArray();
    try {
      bos.close();
      bos = null;
    } catch (IOException ex) {
      System.err.println("Error while decoding BASE64: " + ex.toString());
    }
    return decodedBytes;
  }
  
  private static void decode(String s, OutputStream os) throws IOException {
    int i = 0;
    int len = s.length();
    while (true) {
      while (i < len && s.charAt(i) <= ' ') {
        i++;
      }
      if (i == len) {
        break;
      }
      int tri = (decode(s.charAt(i)) << 18)
          + (decode(s.charAt(i + 1)) << 12)
          + (decode(s.charAt(i + 2)) << 6)
          + (decode(s.charAt(i + 3)));
      os.write((tri >> 16) & 255);
      if (s.charAt(i + 2) == '=') {
        break;
      }
      os.write((tri >> 8) & 255);
      if (s.charAt(i + 3) == '=') {
        break;
      }
      os.write(tri & 255);
      i += 4;
    }
  }
  
  /**
   * 去掉BASE64加密字符串换行符
   *
   * @param str
   * @return
   */
  public static String filter(String str) {
    String output = "";
    StringBuffer sb = new StringBuffer();
    for (int i = 0; i < str.length(); i++) {
      int asc = str.charAt(i);
      if (asc != 10 && asc != 13) {
        sb.append(str.subSequence(i, i + 1));
      }
    }
    output = new String(sb);
    return output;
  }


//    	private static final char last2byte = (char) Integer
//    			.parseInt("00000011", 2);
//
//    	private static final char last4byte = (char) Integer
//    			.parseInt("00001111", 2);
//
//    	private static final char last6byte = (char) Integer
//    			.parseInt("00111111", 2);
//
//    	private static final char lead6byte = (char) Integer
//    			.parseInt("11111100", 2);
//
//    	private static final char lead4byte = (char) Integer
//    			.parseInt("11110000", 2);
//
//    	private static final char lead2byte = (char) Integer
//    			.parseInt("11000000", 2);
//
//    	private static final char[] encodeTable = new char[] { 'A', 'B', 'C', 'D',
//    			'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',
//    			'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
//    			'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q',
//    			'r', 's', 't', 'u', 'validate', 'w', 'x', 'y', 'z', '0', '1', '2', '3',
//    			'4', '5', '6', '7', '8', '9', '+', '/' };
//    	
//    	
//    	public static String encode(byte[] from) {
//    		StringBuffer to = new StringBuffer((int) (from.length * 1.34) + 3);
//    		int num = 0;
//    		char currentByte = 0;
//    		for (int i = 0; i < from.length; i++) {
//    			num = num % 8;
//    			while (num < 8) {
//    				switch (num) {
//    				case 0:
//    					currentByte = (char) (from[i] & lead6byte);
//    					currentByte = (char) (currentByte >>> 2);
//    					break;
//    				case 2:
//    					currentByte = (char) (from[i] & last6byte);
//    					break;
//    				case 4:
//    					currentByte = (char) (from[i] & last4byte);
//    					currentByte = (char) (currentByte << 2);
//    					if ((i + 1) < from.length) {
//    						currentByte |= (from[i + 1] & lead2byte) >>> 6;
//    					}
//    					break;
//    				case 6:
//    					currentByte = (char) (from[i] & last2byte);
//    					currentByte = (char) (currentByte << 4);
//    					if ((i + 1) < from.length) {
//    						currentByte |= (from[i + 1] & lead4byte) >>> 4;
//    					}
//    					break;
//    				}
//    				to.append(encodeTable[currentByte]);
//    				num += 6;
//    			}
//    		}
//    		if (to.length() % 4 != 0) {
//    			for (int i = 4 - to.length() % 4; i > 0; i--) {
//    				to.append("=");
//    			}
//    		}
//    		return to.toString();
//    	}

}  